GHS pictograms, signal words and hazard statements explained

Pick up almost any container of a hazardous chemical and you will see the same building blocks: red bordered diamonds, a single word in bold, and a list of short sentences with codes like H225 and P210. These come from the Globally Harmonized System of Classification and Labelling of Chemicals, the GHS. Once you understand how the pieces fit together, you can read a label or the hazard section of a safety data sheet in seconds.

What the GHS is and is not#

The GHS is a set of criteria and communication rules published by the United Nations. It defines how to classify chemicals by their physical, health and environmental hazards and how to communicate those hazards on labels and in safety data sheets.

The GHS is not a law on its own. Countries and regions adopt it through their own legislation, such as the CLP Regulation in the European Union and the Hazard Communication Standard in the United States. Each jurisdiction chooses which revision of the UN text to follow and may leave out some hazard categories. The UN updates the GHS every two years. This is why the label of the same product can differ slightly between countries, and why exporters need a label and SDS for each market.

Hazard classes and categories#

Classification comes first. The GHS defines hazard classes, such as flammable liquids, acute toxicity or skin corrosion, and splits most classes into categories by severity. Category 1 is always the most severe.

For example, flammable liquids are split by flash point and boiling point:

Once a product is classified, the label elements follow automatically from the classification: the pictogram, the signal word and the hazard statement for each class and category.

The nine pictograms#

GHS pictograms are black symbols on a white background inside a red bordered diamond. There are nine of them.

Precedence rules#

A label shows every pictogram that applies, but some combinations are avoided because they would repeat the same message. Under the GHS and the EU CLP Regulation:

• If the skull and crossbones applies, the exclamation mark is not used.
• If the corrosion pictogram applies, the exclamation mark is not used for skin or eye irritation.
• If the health hazard pictogram applies for respiratory sensitisation, the exclamation mark is not used for skin sensitisation or for skin and eye irritation.

So a label with corrosion and an exclamation mark is telling you about two different hazards, for example corrosivity and acute harmful toxicity.

Workplace pictograms are not transport labels#

Dangerous goods transport uses a different but related labelling system based on the UN Model Regulations. Transport labels are also diamonds, but they have coloured backgrounds and a class number at the bottom. A drum may carry both: GHS pictograms on the product label and transport labels for its dangerous goods class. Our guide to shipping dangerous goods explains the transport side.

Signal words#

The signal word tells you at a glance how severe the most serious hazard is. There are only two:

• Danger for the more severe categories
• Warning for the less severe ones

A label carries one signal word only. If any hazard on the product calls for Danger, the label says Danger. Some low hazard categories have no signal word at all.

Hazard statements#

Hazard statements describe the nature and degree of each hazard in standard wording. Each has a code made of H and three digits:

• H2xx physical hazards, such as H225 Highly flammable liquid and vapour or H290 May be corrosive to metals
• H3xx health hazards, such as H302 Harmful if swallowed, H314 Causes severe skin burns and eye damage or H350 May cause cancer
• H4xx environmental hazards, such as H400 Very toxic to aquatic life or H410 Very toxic to aquatic life with long lasting effects

Some statements are combined, for example H300+H310+H330 Fatal if swallowed, in contact with skin or if inhaled. The standard wording matters because it is translated consistently into every official language of the countries using it.

EU supplemental statements#

The EU keeps a small set of its own phrases with codes starting EUH, such as EUH014 Reacts violently with water or EUH208, which warns sensitive people that a product contains a named sensitising substance. If you sell into Europe, check whether any EUH statement applies to your product.

Precautionary statements#

Precautionary statements tell users how to avoid harm and what to do if something goes wrong. Their codes are P and three digits, grouped by purpose:

A product can qualify for many precautionary statements. Labels normally show a selection of the most important ones (in the EU, normally no more than six), while the SDS can list them all.

Putting it together: reading a label#

Imagine a solvent label showing the flame and exclamation mark pictograms, the signal word Danger, and these statements:

• H225 Highly flammable liquid and vapour
• H319 Causes serious eye irritation
• H336 May cause drowsiness or dizziness

Reading it in order: the product is a category 2 flammable liquid (flash point below 23 °C), it irritates the eyes, and its vapour can make people drowsy. Danger is the signal word because the flammability category calls for it. The precautionary statements will tell you to keep it away from ignition sources, use it in a well ventilated area and protect your eyes.

Where to find the classification#

For a product you are buying, the authoritative source is the supplier's own label and SDS for your market. The classification of a substance can depend on its impurities and its physical form, and mixtures are classified on their composition.

For orientation, official references are useful. In the EU, Annex VI of the CLP Regulation lists harmonised classifications for many substances, and the ECHA classification and labelling inventory shows the classifications that companies have notified.

On CompoundList, chemical safety pages show a GHS classification summary for a first look and always remind you that it is not an SDS.

Common questions from buyers#

Does a product without pictograms mean it is safe? No. It means it does not meet the criteria for any hazard class adopted in that jurisdiction. It can still cause harm if misused, and the SDS may still recommend precautions.

Why do two suppliers' labels differ for the same chemical? Possible reasons include different jurisdictions or GHS revisions, different impurity profiles, different physical forms such as dust and solution, or simply an outdated SDS. Ask both suppliers for their classification basis.

Is the US label different from the EU label? It can be. The US Hazard Communication Standard does not cover environmental hazards, so the environment pictogram is not mandatory there, and the US has a few hazard classes of its own.

Understanding the GHS takes an afternoon. It pays back every time you compare suppliers, plan storage or train a new colleague.